Some I have read on here definitely came into poly when there was a problem with the primary relationship. Problems of compatibility or interests or even communication-style. Of course once they were in it, some primary relationships- the ones with a good foundation where the partners are strong individuals have survived the transition from mono to non-mono. I do think that it is fair to say some enter into poly in a less than ideal way, however, if it can help the individuals be happier as individuals with a new ability to connect with others in ways they were not previously connecting, then it is possible for that patchwork to find some support in the "batting" that poly can offer a weakened relationship. Sometimes...not always. There are numerous examples where poly for a weak relationshp has completely shattered the primary relationship. but again, I have to say that poly is never the cause of the breakup from my observation on here and other sites, but rather a grasping at straws. It isn't ENOUGH to keep a bad relationship together. Know what I mean?